The objective of this project is to develop a system to detect induced mutations in mice by using high speed rate analyzers to monitor the thermal stability of enzymes. Pilot experiments are in progress to determine the biochemical conditions necessary to screen crude homogenates of mouse tissues for thermal stability mutants of 20 enzymes. Preliminary results indicate that enzyme heat denaturation is closely correlated to pH, ionic strength, and endogenous concentrations of substrates and cofactors. In addition naturally occurring variants of isocitrate dehydrogenase and phosphoglucose isomerase have been found to be detectable with heat stability techniques.